1. Field of the Present Invention
The present invention relates to an angular rate producer, and more particularly to an angular rate producer with microelectromechanical system (MEMS) technology to measure vehicle angular rate. The angular rate producer of the present invention comprises an vibrating type angular rate detecting unit, an interfacing circuitry, and a digital processing system to obtain more highly accurate, sensitive, stable vehicle angular rate measurements under dynamic environments.
2. Description of Related Arts
Generally, an angular rate producer can function as an angular rate sensor or a gyro. It can obtain vehicle angular rate measurements to employ a conventional gyro in the vehicle. Many types of approaches based on various sensing principles used to achieve an angular rate sensor have been invented in the past decades, are currently being invented, and will continue to be invented as commercial markets for angular rate sensors continue to expand.
Existing angular rate sensors or gyros include spinning iron wheel gyros and optical gyros.
Conventional spinning iron wheel gyros are principally based on the Gyroscopic Law. The spinning iron wheel gyros generally have a spinning wheel and analog output, high cost, were heavy, consumed a lot of power because they had moving mechanical parts, and wore out after just a few thousand hours of operation.
Existing optical gyros, including ring laser gyros and interferometric fiber-optic gyros, are dependant on the Sagnac Effect. The optical gyros generally have digital output and moderate cost.
Truly low-cost, highly producible, miniaturized size, and low power angular rate sensors with extended life have been a goal of the industry for many years. Conventional angular rate sensors have been commonly used in wide variety of applications. However, their cost, size, and power prohibit them from the emerging commercial applications, including phased array antennas.
Rapid advance in MEMS technologies makes it possible to fabricate a low cost, light weight, miniaturized size, and low power angular rate sensors. "MEMS" stands for "MicroElectroMechanical Systems", or small integrated electrical/mechanical devices. MEMS devices involve creating controllable mechanical and movable structures using IC (Integrated Circuit) technologies. MEMS includes the concepts of integration of Microelectronics and Micromachining. Examples of successful MEMS devices include inkjet-printer cartridges, accelerometers that deploy car airbags, and miniature robots.
Microelectronics, the development of electronic circuitry on silicon chips, is a very well developed and sophisticated technology. Micromachining utilizes process technology developed by the integrated circuit industry to fabricate tiny sensors and actuators on silicon chips. In addition to shrinking the sensor size by several orders of magnitude, integrated electronics can be placed on the same chip, creating an entire system on a chip. This instrument will result in, not only a revolution in conventional military and commercial products, but also new commercial applications that could not have existed without small, inexpensive inertial sensors.
Some MEMS angular rate sensor approaches have been developed to meet the need for inexpensive yet reliable angular rate sensors in fields ranging from automotive to consumer electronics, based the concept of using a vibrating element to sense angular rate under the Coriolis principle. For example, single input axis MEMS angular rate sensors are usually based on either translational resonance, including tuning forks, or structural mode resonance, including vibrating rings and associated microelectronic supporting circuitry. Moreover, dual input axis MEMS angular rate sensors may be based on angular resonance of a rotating rigid rotor suspended by torsional springs. The inherent symmetry of the circular configuration allows angular rate measurement about two axes simultaneously.
Unfortunately, there is not a high performance commercial MEMS angular rate sensors available, which can compete with the measurement accuracy of conventional iron gyros and optical gyros. It is still much more of a challenging to design and manufacture a MEMS angular rate sensor with sufficient accuracy, keen sensitivity, wide dynamic range, and high stability.